The present invention relates to a method for press working metallic materials by making use of transformation super-plastic phenomena.
Heretofore, in press working of a workpiece made of metallic material such as, for example, stainless steel, for the purpose of increasing the working speed, a method has been generally practiced in which cold working is conducted with a kind of sandpaper sandwiched between a die surface and a workpiece surface. However, such cold press working in the prior art has often encountered disadvantages such that depending upon the sand grain size of the sandpaper sandwiched between the die surface and the workpiece surface, a crack may be generated in the formed portion of the workpiece, especially at a portion relatively larger curvature or a locally thick portion is apt to the produced; and that generation of corrugations may be generated and other problems may occur.
In addition, in the conventional forging process, a very large forging, energy is necessitated and there exists a problem that upon forging loud noise is generated.
The inventor of the present invention had been continuing various experimental researches on the super-plastic behavior of metallic materials, and during that period of time it had been discovered that in relation to the existence of a transformation point in an equilibrium state diagram of metals, metallic material would be elongated with a low stress just as wheat-gluten bodies are under specific conditions. The present invention has been proposed on the basis of the above discovery.